IBM TS4500 Introduction And Planning Manual page 58

Your library configuration is not limited to the examples shown in Figure 11 on
page 41. Many configurations are possible, and you can design them according to
your business needs.
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IBM TS4500: Introduction and Planning Guide
– Configuring a single logical library to communicate with multiple servers
through multiple control paths. This configuration (see example 4 in
Figure 11 on page 41) requires that you add control paths. It is used by
Backup, Recovery, and Media Services.